German patent application DE 198 05 843 A1 discloses a hydraulic unit for a slip-controlled brake system comprising a block-shaped accommodating member which has eight valve accommodating bores in total, arranged side by side in a first and a second valve row, with electromagnetically operable inlet and outlet valves inserted in said bores. Outside the two valve rows are a pump accommodating bore and two parallel accumulator accommodating bores. The accumulator accommodating bores are arranged paraxially relative to the valve accommodating bores and laterally to the two valve rows, while the pump accommodating bore extends in parallel to the two valve rows. Disposed centrically between the two accumulator accommodating bores is a motor accommodating bore that extends paraxially relative to the accumulator accommodating bores into the pump accommodating bore. Further, there is provision of a third valve row which opens into the housing surface of the accommodating member at the other end thereof, remote from the braking pressure generator ports and the first and second valve rows. The third valve row, which is thus arranged directly adjacent to the two accumulator accommodating bores, ensures a simple functional extension of the hydraulic unit configured for anti-lock pressure control for the purpose of traction slip control or driving dynamics control. To this end, magnetic valves designed as electric change-over valves and closed in their initial position are inserted into the two external valve accommodating bores. Separating valves open in their initial position are inserted in the form of magnetic valves into the two intermediate valve accommodating bores of the third valve row.
The large distance between the braking pressure generator ports and the electric change-over valves, however, is disadvantageous because correspondingly long suction channels from the braking pressure generator via the electric change-over valves to the pump accommodating bore are necessary for the purpose of pressure fluid supply to the pump by way of the change-over valves. Inevitably, it is also complicated to evacuate the suction channels and to fill them with brake fluid, which is due to the high volume take-up. In addition, a correspondingly high hydraulic resistance is probable during pump operation. The necessary long suction channels can only be made by complicated drilling operations under aspects of manufacture.
In view of the above, an object of the present invention involves improving a hydraulic unit of the indicated type in such a way that the above-mentioned drawbacks are overcome.